Electrostatic precipitators utilizing a plurality of axially spaced collector plates, which plates are alternately of opposite charge, have been used for removing dust and other foreign particles from gases, such as air. Conventional precipitators, as disclosed in U.S. Pat. Nos. 3,871,974 and 2,776,724, have employed collector plates of equal outside diameter, which plates have central openings which are either of equal diameter or are of progressivley decreasing diameter. While these precipitators have been partially effective in removing foreign particles from gases, nevertheless they have not removed foreign particles with the speed and efficiency required to permit the mass handling of large quantities of highly contaminated gases per unit time.
In studying these known precipitators, it was discovered that one of the primary problems was the nonuniformity of flow between the plural pairs of oppositely charged collector plates, and the nonuniformity of the collection capability of the various pairs of oppositely charged plates. Since the plates are axially spaced along the precipitator, and inasmuch as the inflowing air is supplied axially into one end of the precipitator so that it must be turned to flow radially outwardly between the plates, the air does not flow equally between all of the adjacent pairs of plates. Rather, substantially greater quentities of air flow between the plates adjacent the closed end of the precipitator in contrast to the amount of air which flows between the plates adjacent the inlet end. Thus, only a small portion of the axial length of the precipitator operates at maximum efficiency, so that maximum flow rate and particle removal capacity of the precipitator is severely limited.
To correct this nonuniform flow between the adjacent plates, it has been proposed to form the plates with progressively decreasing central openings so that the precipitator has a central gas-receiving space which is of a tapered and converging configuration. While this does tend to equalize, or at least make more uniform, the flow rate of gas between the adjacent pairs of plates, nevertheless this configuration results in the plates adjacent the closed end of the precipitator being of greatly increased surface area in contrast to the plates adjacent the inlet end. Since the same potential difference is applied across each pair of adjacent plates, electrostatic fields of different intensity are created throughout the length of the precipitator. Further, these larger area plates are believed to result in increased turbulence when the air flows between the plates, which turbulence reduces the particle removal efficiency.
Accordingly, the present invention relates to an improved electrostatic precipitator having a plurality of axially spaced plates which are alternately charged to form electrostatic fields therebetween, which plates are of a ringlike configuration and have inner diameters which, either progressively or in a steplike manner, are of decreasing diameter so that the central gas-receiving space is of decreasing diameter to result in substantially uniform flow of gas radially outwardly between the oppositely charged pairs of plates. The outer diameter of the plates are also of decreasing diameter, either progressively or in a steplike manner, as the plates extend toward the closed end of the precipitator so that all of the collector plates are of substantially equal surface area, whereby a substantially uniform electrostatic field is created between each pair of adjacent plates.
Another object of the present invention is to provide a precipitator, as aforesaid, wherein the collector plates are formed as a rotor which is rotatably driven to assist in causing the air to flow outwardly between the plates due to centrifugal force, which centrifugal force also assists in removing the collected masses of solid particles from the plates to assist in keeping the plates clean.
It is also an object of the present invention to provide an improved precipitator, as aforesaid, which can be manufactured and assembled in an economical manner, requires a minimum number of different plate sizes, is durable in operation, permits the flow therethrough of large quantities of gas per unit time, and can be operated by a minimal amount of energy.
Other objects and purposes of the present invention will be apparent to persons acquainted with devices of this type upon reading the following specification and inspecting the accompanying drawings.